Recently, vertical alignment mode (VA mode) liquid crystal display devices and transverse electric field mode liquid crystal display devices (including IPS mode devices and FFS mode devices) are used as liquid crystal display devices for TV applications and the like. Note that the transverse electric field mode is sometimes referred to as “IPS mode”.
Of the above device types, the VA mode liquid crystal display device exhibits a large viewing angle dependence of the γ characteristic as compared with the IPS mode liquid crystal display device. The γ characteristic is an input grayscale level vs. luminance characteristic. In general, the viewing direction (i.e., viewing angle) is expressed by the angle with the normal to the display surface (polar angle) and the azimuthal angle that represents the azimuth in the display surface. The γ characteristic of the VA mode liquid crystal display device particularly has a large dependence on the polar angle of the viewing direction. That is, the γ characteristic that is acquired when viewed from the front (in a direction normal to the display surface) and the γ characteristic that is acquired when viewed in an oblique direction are different from each other, and therefore, the grayscale display state varies depending on the viewing direction (polar angle).
To reduce the viewing angle dependence of the γ characteristic in the VA mode liquid crystal display device, a liquid crystal display device having a multi-pixel configuration such as disclosed in Patent Document 1 of the present applicant, for example, has been put to practical use. The multi-pixel configuration refers to a configuration in which one pixel includes a plurality of sub-pixels of different brightnesses. Note that, in this specification, the “pixel” refers to the minimum unit of display in the liquid crystal display device. In the case of a color liquid crystal display device, the “pixel” refers to the minimum unit of display of each primary color (typically, R, G, or B) and is sometimes referred to as “dot”.
Each of the pixels of a liquid crystal display device having a multi-pixel configuration includes a plurality of sub-pixels among which different voltages can be applied across the liquid crystal layer. For example, when a pixel displays at least an intermediate grayscale level, the pixel includes two sub-pixels which exhibit different luminances. When two sub-pixels constitute one pixel, the luminance of one of the two sub-pixels is higher than a luminance that the pixel is to display (bright sub-pixel), and the luminance of the other sub-pixel is lower than the luminance that the pixel is to display (dark sub-pixel).
The multi-pixel configuration is also referred to as “pixel-divided configuration”, and various types thereof have been known. For example, each of the pixels of a liquid crystal display device shown in FIG. 1 of Patent Document 1 includes two sub-pixels, and different display signal voltages are supplied to the two sub-pixels via two source bus lines (display signal lines) respectively corresponding to the two sub-pixels. Here, this type is referred to as “source direct multi-pixel type”.
On the other hand, in a liquid crystal display device shown in FIG. 12 of Patent Document 1, two sub-pixels of each pixel are supplied with equal display signal voltages. Here, as shown in FIG. 12, each sub-pixel has a storage capacitance, and a storage capacitance counter electrode (connected to the CS bus line) which forms the storage capacitance is electrically independent in each sub-pixel. The voltage supplied to the storage capacitance counter electrode (“storage capacitance counter voltage”) is changed after the TFT is switched from ON to OFF, whereby effective voltages applied across the liquid crystal layer of the two sub-pixels are made different from each other with the utilization of capacitance dividing. Here, this type is referred to as “CS swing type”. The CS swing type has such an advantage that the number of source bus lines can be reduced as compared with the source direct type. In the case where each pixel includes two sub-pixels as illustrated, in the CS swing type, the number of signal lines can be halved as compared with the source direct type.
Using such a multi-pixel configuration enables improving the viewing angle (particularly, polar angle) dependence of the γ characteristic of a liquid crystal display device (particularly, VA mode liquid crystal display device). However, there is such a problem that even when the viewing angle dependence of the γ characteristic is improved, the viewing angle dependence of the color reproducibility cannot be sufficiently reduced.
Patent Document 2 of the present applicant discloses a liquid crystal display device in which, for the purpose of reducing the viewing angle dependence of the color reproducibility, the area ratio and/or lighting time of the bright sub-pixel in each of the primary color pixels (typically, red (R) pixel, green (G) pixel and blue (B) pixel) is adjusted so as to reduce the viewing angle dependence of the color reproducibility of a human skin color (hereinafter, “skin color”).